I am trying to design a rim brake road bike to clear 700x30mm tires (690mm diameter). Does anyone have any practical experience locating the bridge height?
The information is scarce because the last time rims brakes were produced, 700x28 was considered the biggest size
Note: The CAD shown is a 700x30 + 6mm of clearance. So technically the tire won’t rub the bridge, but I would not call it safe.
Questions:
Is the location the documentation calls out for the caliper with the pads in the middle of the brake arms?
Would bumping the bridge up 5mm (358mm) go out of range of adjustment?
Does anyone have any experience locating the bridge to clear bigger tires?
Bonus Questions: Calipers that clear 700x30?
Are there any mid reach (<50mm) calipers that can take 30mm tires? The only brake I could find that officially clears 700x30 are the Cane Creek eeBrakes.
Are there other brakes out there?
Are there any unofficial 700x30 clearance brakes?
Thanks everyone, let’s make rim brakes great again.
TRP and Velo Orange both make mid reach calipers. Potentially TRP actually make teh Velo Orange ones for them.
For mounting and 28-30 mm tyres I go for a 357-358mm distance but you should also check the underside of the brake caliper as some have more bulk around the bolt/pivot than others. For frames that are intended for 25-28mm I was using 356 and have a non adjustable jig to check locating when cutting the bridge in.
For road frames using standard reach brakes (39-49mm of reach on the arms) I put the brake bridge at 358mm from the center of the dropouts. This will easily clear a 28mm tire and often a 30mm tire depending on the tire/rim combo. When building frames with mid reach brakes (49-59mm of reach on the arms) I bump that 358mm up another 9-10mm. As mentioned, Velo Orange and TRP have brakes that fit this use case. This affords clearance for a 35mm tire easily but I have often gotten away with a 38mm. Here is a picture of the TRP brakes over a Compass/RH Knobby 38mm tire.
Thinking out loud, to bring brake calipers to “modern” road bike standards (28-32mm), I think we need a “short-mid” reach caliper (43-53mm). I know, splitting the difference
Maybe the easier route would be a CNC brake shoe that moves the pads down 2-3mm:
What might also help is a wider rim brake rim (23mm internal 26mm external). This would better support the 30mm tire and move the brake arms “wider”. I have chatted with Jimmy at Astral, and they are capable of producing a wider extrusion to update their Elan Wheel.
Sadly, the brakes and rims are a solvable problem with $30k of investment. The limiting factor will be rim brake groupsets. The big groupset manufacturers are killing off their performance mechanical rim groupsets. Ebay Supply of Shimano Ultegra groupsets can only last so long!
Here’s another option for brake calipers. I’ve had older ones that were some of the nicest calipers I’ve ever had. I don’t have any real world experience with the newer generation but there is a claim of 32mm tire clearance.
The TRP mid-reach brakes are really nice. As others have said, they can clear a 35mm no problem. My last road bike used them with 32s with the pads in the middle of the slots.
Extending the brake arms kind of works - I have seen this done to use 650C wheels in a 700C fork before. But it changes the mechanical advantage of the brake, and can be a loss of power - just being at the very bottom of the slots is a noticeable difference in feel. The original EE brake used an eccentric mounting bolt to adjust for pad height so that the leverage at the pads was maintained as Craig intended.
I have had success with using direct mount brakes to clear 32mm tires. I positioned the bosses at 339mm height instead of 337. This was using the EE DM brake, which has good clearance underneath - sadly they have stopped making those…
The TriRig Omega brake has a lot of adjustment and lots of room underneath it. The previous ones I found to be a bit lacking in modulation; I don’t know if this has improved in the latest version. I’m guessing these would clear a 32mm with the correct boss positioning.
I guess since we are going down this rim brake rabbit hole, It makes sense to look at direct mount.
Just like the single bolt mount rim brake, the direct mount brake’s max 28mm clearance is very limiting. The offender seems to be the width of the posts. The 49mm spacing does not leave much room for a tire.
With the EE brake, Craig and I went further than 32mm - he knew that with the DM system he could retain the leverage and stiffness of the standard brake, so we decided to maximise tire clearance. Thus the prototype brakes will clear a 44mm tire, or lots of room for a 38mm with fenders.
We used 68mm for the DM boss width, at the previous standard 337mm from the axle. The brakes work really well (feel the same to me as the standard EE brake). […] I had a few other builders express interest - the boss at Cane Creek has indicated that he would be willing to have a batch of brakes made if there were some pre-orders.
Rob makes a great point about the mechanical advantage. If you try to move the DM bosses higher to get clearance, you end up decreasing the leverage on the caliper. Bigger tires need more stopping power.
This leads me to think that if we want the direct mount to continue, we need a new standard for post width:
Current: 49mm
Proposed Road: 55mm (32mm tires)
Proposed Gravel 68mm (44mm tires)
I need to check if those post widths make sense for forks and road bike seat stays. What do you guys think? In order to make the economics of a new direct mount standard brakes and forks work out, we would probably need 20 builders to produce 5 rim brake bikes each.
My take and preference is no rim brakes for serious gravel bikes but rim brakes for road tyres up to say 32ishmm would be great. Rim brakes work awesome but the wear and tear on the rims and the cost or replacement rims is a issue for me.
I like fat tires for comfort and I like the idea of rim brakes for the ability to use them on compliant steel fork.
@englishcycles have you used the Paul Racer or Racer M and could you compare the braking ability with the custom EE Brakes you’ve used?
I expect the EE Brakes are lighter (and lighter bosses on the frame too) but I’m curious about function?
Do you know the weight of those brakes? I’d be curious to see how they’d compare to a Paul Racer or Rene Herse centerpull.
The Paul Brakes are very nice looking and available. I have a bike with brazed-on Racers and they seem great to me.
Also, one can buy longer arms meant for EEBrakes for Bromptons on AliExpress which I gather need about 8mm more reach. I wonder how that functions as a mid-reach brake.
Finally, I’ve heard all sorts of varied reviews on Ciamillo stopping power and business dealings over the years but noticed they make some longer reach brakes for Bromptons.
It’s hard to say what might exist out there in the long run if spare brakes or parts were ever needed but there are a lot of options out there now to accommodate fat tires and rim brakes. It would be nice if the mounting were standardized but it’s hard for me to imagine that could happen now unless new brakes were made to work with an existing brake mounting standard.
@Daniel_Y two new standards seems like a lot! For me, bigger is better so start with the gravel standard. You can always run smaller tires with that extra clearance.
I hear you! Ideally, we have the freedom and resources to build the bikes the way we want (rim brakes for all!). I am coming at this from a consumer/business angle. In my opinion, the missing pieces: brakes, forks, rims, and groupsets need some commercial success to reach a scale to be financially viable (qty 100-200). While I am grateful that Cane Creek might be willing to produce qty 10 brakes, a $800 pair of brakes won’t be viable in the long run. A $150 pair of forged brakes would be much more reasonable.
I get way more requests for rim-brake road bikes than rim-brake gravel bikes. Granted, that might not be the case for every region and every builder, so we can see which one gains the most traction.
From the 5000ft view, I think a new road direct mount standard (DM55) can have mainstream commercial success. Entry-level road bikes (<$2000) should be coming with direct-mount rim brakes and 30-32mm tires instead of disc brakes. In comparison, rim brakes would be much lighter, cheaper, easy-to-own, and robust, which equates to more fun.
Poking around with DM55
This picture illustrates the problem we are dealing with:
@Daniel_Y This is great! I’m all for better brakes for bigger tires.
Why direct mount, which is to say why not just use the already available and standardized center mount mid reach brakes? The brakes and forks are available from a number of manufacturers.
Direct mount brakes should be stiffer and can be made lighter, but direct mount short reach brakes never totally replaced center mount brakes. Cane Creek discontinuing the direct mount eeBrakes surely speaks to this as well.
Are the advantages of a direct mount mid-reach brake good enough that manufacturers making rim brake bicycles would adopt this rather than moving a brake bridge 1cm and lengthening fork legs 1cm?
The Paul Racer M in braze-on form is a direct mount mid-reach brake. Would its mounting bosses be acceptable as a standard? It’s certainly easier to start making bikes for this with the brakes readily available.
What about classic centerpull bosses for an existing standard? I think there were two standard placements one for mafac racer-like brakes and one for mafac RAID (and now Rene Herse).
Finally, why optimize for 32mm tires instead of 35 or 38? Wouldn’t going bigger future proof this concept a bit?
I am visualizing the DM55 standard (lets call it that) as a pure performance road bike setup. I know there are blurred lines between road, allroad, and gravel, but to me and my personal experience, anything over 30mm starts getting too slow. Also, I found that riding a high-performance road tire for “light gravel” is not realistic, just ask my Vittoria N.EXT tires (RIP).
With direct mount, ideally, the bosses need to land directly on the fork blade and seatstays. That means if you start with a wider standard for wider tires, the pure road bikes are going to have wide fork legs and seat stays.
Rob mentioned this a bit earlier, one downside would be leverage. The cable pull/lever throw of road brifters is not going to change, so if you lengthen the caliper arms to get more clearance, you end up decreasing your overall lever-to-brakepad leverage ratio.
Direct mount can get around this because the caliper pivots and arms don’t need to change location. I am sure there are going to be some compromises to get the bigger clearance, but I think for the most part, the tire clearance is decoupled from the braking leverage.
The Paul Racer is a good callout and a great precedent of a new standard and custom brake that goes with it.
With a 63mm width and 340mm height, it looks like it is already a good direct-mount gravel standard (DM63).
However, I would argue that given that the brake and DM63 standard have been around for a while and have not gained traction, there is something about the brake that does not appeal to consumers. Granted, the same thing could be said for a DM55 standard for pure road bikes as well.
I’m all for rim brakes on road bikes. The big advantage in my eyes is the ability to use a steel fork with slim blades to provide some added cushion that the narrow tires cannot provide.
@Daniel_Y Have you tried riding the mid-reach brakes from TRP or Velo Orange? They’re really nice. If you want, I’ll lend you my TRPs for you to test. I have a carbon fork you can use too. You just need to build a frame.
It seems like a lot of effort to create a whole standard and get a really expensive brake made when there are good options already available.
The first bike I made was a rim brake road bike. I had planned to use EE brakes front and rear, but I messed up the placement of the bridge on the rear by enough that I had to use a mid-reach brake. So now I’ve got EE in the front and VO in the rear, and I think they’re mostly on par with each other in terms of performance. To me that’s saying something as I consider the EE brakes to be the best rim brakes out there.
I’ve also used the Racer M, but I could never get them set up well enough to the point where I’d consider them on par with either the EE or the VO. The error was probably mine though.
The next bike I build will be a rim brake w/ 30mm clearance and regular single pivot calipers to test it out. If that works, I can explore the caliper DM caliper question.
